Modern-day turbine engines often use an electronic control system to monitor and control the numerous functions associated with engine operation. Some turbine engines have a gear fixedly mounted on the engine shaft and a magnetic transducer, or the like, may be positioned adjacent the gear to derive an electrical signal sinusoidally related to the passage of each gear tooth. Since the number of teeth on the gear is known, the periodicity of the sinusoidal signal can be directly related to the rotational velocity N.sub.1 of the turbine engine, one of the many parameters important to engine operation.
Trim balance of the turbine engine is particularly significant for ensuring smooth, vibration-free operation of the turbine engine. In this type of dynamic balance, the angular position of a reference mark on the rotating shaft or other rotating portion of the engine must be related to a mechanical imbalance so that weight can be either added to, or removed from, the rotating member. A simple and inexpensive angular reference has been a "short tooth", i.e., a tooth on which a small amount of material has been removed, such as 0.020 inch from the tip of the gear tooth.